Deleting a class I made by mistake

How do you delete a class that I made by mistake? I made it months ago and never populated or assigned anyone to the class I can't seem to get rid of it. also made some custom classes for 2016. Now with the new year upon us I need to delete those custom classes. Also what does it do when you set a class to default?

Click the pencil icon next to the name and choose combine with ... to combine it back to the class it was split from. Or if it was not a split class you will have the option to Remove Class